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(No Model.) 5 SheetsSheet 1.

0. D. ROGERS. DIE FOR ROLLING scmzw THREADS.

No. 430,237. Patented June 17, 1890.

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5 Sheets Sheet G. D. ROG DIE FOR ROLLING so W THREADS. No. 430,237. Patented June 17, 1890.

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0. 1). ROGERS DIE FOR ROLLING SCREW THREADS.

N0. 430,237. Patented June 1'7, 1890.

\ UNITED STATES PATE T OFFICE.

CHARLES D. ROGERS, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO THE AMERICAN SCREIV COMPANY, OF SAME PLACE.

DIE FOR ROLLING SCREW-THREADS.

SPECIFICATION forming part of Letters Patent No. 430,237, dated June 17, 1890.

4 Application filed January 28, 1890. Serial No. 338,395. (No model.) I

To all whom it may concern:

Be it known that I, CHARLES D. Roenns, a citizen of the United States, residing at Providence, in the county of Providence and State 5 of Rhode Island, have invented certain new and useful Improvements in Dies for Rolling Screw-Threads; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable to others skilled in the art to which it appertains to make and use the same, reference bein g had to the accompanying drawings, and to letters and figures of reference marked thereon, which form a part of this specification.

My present invention has relation to dies for forming screw-threads upon screws, more,

especially wood-screws, by rolling the screwblanks between them, the action of the latter, when properly mounted and operated, causing the metal to raise radially from the body of the blank to form the threads.

he invention herein described and claimed is an improvement upon the die patented to me September20, 1887, by United States Patent 2 5 No. 570,85. In that die the series of inclined grooves and ribs were made parallel to each other, the obliquity of the ribs and also the angle of the sides thereof being constant from one end to the other. The action of such former dies was to force the ribs into the screw-blank to the required maximum depth at the commencement of the operation,thereby limiting the pressure toward the axis to a comparatively small degree; the continued movement of the dies caused the metal between the ribs to be more and more compressed laterally, and at the same time radially expanded into the grooves of the dies until at the end of the operation it fills them,

the thread then being homogeneous or solid and a counterpart of the grooves at the end of the dies. As the metal between the ribs expands radially during the progress of the rolling, the diameter of the blank measured across the threads increases, and by reason of this increase of the diameter a longer portion of the die is required, as the rolling progrosses, to give a complete revolution to the blank, and inasmuch as the distance between the central line of the threads of a screw is constant, and consequently the distance between the central line of the ribs of the dies is constant, it is necessary, when the length of the die required for one revolution of the blank is increased, that the angle of the ribs of the die with its line of motion should be reduced. Unless this is done there is a tendency to move the blank across the dies, and in the ordinary way of arranging the dies to raise the conical point of the blank away from the inclined portions of the faces of the dies which form the point of the screw, and produce an imperfect thread. An unnecessary strain is also brought upon the dies, which sometimes results in breaking them. I have found that I can remedy these difficulties by changing the pitch or inclination of the ribs and grooves of the dies to correspond with the increasing diameter of the blank as the rolling progresses. Theoreti- 7o cally this change of the inclination should be constant, so that the ribs would present curves, but for practical purposes it is sufficient and much easier to make the dies in sections with a different inclination of the ribs corresponding to the increase of the diameter of the blanks. A revolution of the blank does not correspond precisely with the circumference of the edges of the threads at diiferent stages of the rolling but to a circumference interme- 8o diate between that and the circumference of the bottom of the groove.

My improved die is represented in the annexed five sheets of drawings, in which- Figure 1, Sheet 1, shows a front view of the working'face of a die having straight inclined parallel ribs and grooves, the inclination being constant from one end to the other. Fig. 2 is a similar view showing one example of my improved die. As drawn, the die is 0 formed of four pieces or sections, the obliquity or inclination of the ribs and grooves of one section varying somewhat from those of the adjoining section, as may be readily determined by placing the drawing horizontally in front of the eye and nearly level therewith and ranging across the figure. Fig. 3, Sheet 2, is another example of my improved die. In this drawing, however, the ribs and grooves have a curved form, the roe angle of which with the line of movement of the die is constantly varying, the entire die being in one piece. Fig. 4: is a top or edge View showing successive groov'es along the edge and the increasing distance between them measured lengthwise and the increasing width of the top of the ribs. Fig. 5 is a longitudinal sectional view taken through the bottom of one of the grooves. Fig. 6 represents a die the same as shown in Fig. 3, except that it is in four pieces or sections. Fig. 7 is a diagram introduced tween the former method of arranging the ribs and my improved way of disposing them. Fig. 8, Sheet 3, shows in elevation a piece of a screw-blank greatly enlarged be- ,fore being subjected to the action of a pair of screw-threading dies. Fig. 9 represents the same in section during the screw-threading operation, the ribs of the dies being impressed into the metal to the required full depth and corresponding say to a section taken through the blank and dies at the end of the first half-revolution of the blank, when both dies are made to reciprocate. Figs. 1O, 11, 12, 13, and let represent similar sectional views showing the progressive development of the screw-thread and the increase of diameter. Fig. 15, Sheet 5, shows 'sectionally the fully-developed screw-thread resting in the dies at the end of the operation. Fig. 16 is a View of the front end of a die in reduced scale, adapted to roll a gimlet-pointed woodscrew. Fig. 17 represents the opposite end of the die. Fig. 18 shows in cross-section a pair of such dies at the completion of the screw-threading operation, having a screw retained between them; and Fig. 19 is an enlarged sectional view of a rolled-thread woodscrew cut through its longitudinal axis.

In the several figures the parts marked r indicate the ribs or bars of the dies, and g the grooves between the ribs.

A designates my improved die-that is, a die having the inclination or obliquity of the ribs and grooves variable or changing from one end of the die to the otherwhile A, Fig. 1, indicates a die having straight inclined grooves and ribs, substantially as common to former construction of dies, wherein the amount or degree of inclination of the ribs is uniform from one end of the die to the other end.

I would state that the several dies represented in Sheets 1 and 2 of the drawings, as drawn, would roll the screw-thread 0 only on the straight or cylindrical part of a rod or blank, the face of the ribs of the die transversely being fiat.

In order to produce gimlet-pointed screws a, (see Sheet 5 of the drawings,) the general contour of the face of the dies transversely would be modified accordingly, as indicated in Figs. 16, 17, and 18, at the upper and lower edges of the dies, wherein the ribs 0' and grooves g. are adapted to produce upon the to show graphically by comparison the dilference bepoint portion 19 of the blank a screw-thread c, Fig. 19, having a constantly diminishing depth toward the point. In the drawings I have represented 'cross-sectionally what I consider to be the best form for the grooves and ribs. The face of the ribs is thin and slightly truncated at the entering or front end where the rolling commences and much wider at the opposite end, the angle of the two sides of the ribs being alike and constant from one end to the other, as stated in my United States patent before referred to. In forming the threads of a screw by means of a pair of these dies, the thin ends of the ribs are forced directly into the metal of the body I) of a blank at the commencement of the operation to the maximum depth required, and as the rolling progresses the metal is more and more compressed between the ribs, and gradually expands into the grooves of the dies until atthe end of the operation it fills them, and the thread is completed.

A manner of forming the grooves g of the die A (shown in Fig. 1) is to place the steel blank (annealed) upon the table of a suitable milling-machine and then block it up to the desired angle and secure it in place. The machine is further provided with a revolving arbor carrying a milling tool or cutter or a series of cutters, having transversely the counterpart of the grooves to be produced. Now upon feeding the table ahead slowly the revolving cutters will cutaway the blank and form ribs 1, the angle of its sides being constant from one end of the die to the other. The die, after being hardened, is then ready for use:

The die shown in the other figures may be cut in a similar manner to that just described, except that a cam or former may be employed to give an endwise movement to the revolving cutting-arbor corresponding to the varying obliquity or inclination of the grooves and ribs coincident with the travel of the table.

By referring to the diagram represented in Fig. 7 the light diagonal line m indicates, say, the center of a rib or groove of a die, the inclination being constant from its comm encement to the end of the die, substantially as common to dies formerly made. In said Fig. 7 the vertical distance between the horizontal lines n indicates the corresponding or axial distance between the screw-threads produced by a pair of suitably-operated dies. It will be seen that as the inclination of the ribs m is constant, the horizontal divisions being alike, the several intersections of the lines or and m will be equidistant; therefore, the horizontal distance between the corresponding ordinates 1 2 3, 850., along the upper edge of the figure are also equal; but, as the metal of the blank between the ribs is continuously rising during the process of forming the screw threads, it follows, as before stated, that each succeeding revolution of the blank on its axis should travel an increased distance. This increase I have endeavored to indicate by the IIO heavy line m, which corresponds relatively with the line m, just described. The curved line m, Where it intersects the lines n, it will be seen, cuts it at unequal points, the resulting series of ordinates 1 2 3, 850., being indicated at the lower edge of the figure. Assuming now that the horizontal distance along the die from the commencement 0 to the first ordinate 1 represents, say, one-half the circumference of the blank at the root of the screw-thread, the successive bottom ordinates 2, 3, 4, 5, 6, and 7 indicate the correspondingly-increasing circumference of the screw due to the gradual development of the thread, the length of the divisions gradually increasing in a corresponding ratio, although the diameter 12 of the screw at the bottom of the thread remains practically the same throughout the operation, as represented by Figs. 9 to 15.

It will be seen that an ordinary die, as

ishes continually or by sections toward the finishing end of the die to correspond with the increasing diameter of the threads of the screw.

In testimony whereof I have affixed my signature in presence of two Witnesses.

CHARLES '1). ROGERS.

Witnesses:

CHARLES HANNIGAN, GEo. H. REMINGTON. 

